[llvm] r322986 - [SystemZ] Implement computeKnownBitsForTargetNode

[Ulrich Weigand via llvm-commits]

Author: uweigand
Date: Fri Jan 19 12:49:05 2018
New Revision: 322986

URL: http://llvm.org/viewvc/llvm-project?rev=322986&view=rev
Log:
[SystemZ] Implement computeKnownBitsForTargetNode

This provides a computeKnownBits implementation for SystemZ target
nodes.  Currently only SystemZISD::SELECT_CCMASK is supported.


Modified:
    llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.cpp
    llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.h

Modified: llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.cpp?rev=322986&r1=322985&r2=322986&view=diff
==============================================================================
--- llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.cpp Fri Jan 19 12:49:05 2018
@@ -5496,6 +5496,30 @@ SDValue SystemZTargetLowering::PerformDA
   return SDValue();
 }
 
+void
+SystemZTargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
+                                                     KnownBits &Known,
+                                                     const APInt &DemandedElts,
+                                                     const SelectionDAG &DAG,
+                                                     unsigned Depth) const {
+  unsigned BitWidth = Known.getBitWidth();
+
+  Known.resetAll();
+  switch (Op.getOpcode()) {
+  case SystemZISD::SELECT_CCMASK: {
+    KnownBits TrueKnown(BitWidth), FalseKnown(BitWidth);
+    DAG.computeKnownBits(Op.getOperand(0), TrueKnown, Depth + 1);
+    DAG.computeKnownBits(Op.getOperand(1), FalseKnown, Depth + 1);
+    Known.Zero = TrueKnown.Zero & FalseKnown.Zero;
+    Known.One = TrueKnown.One & FalseKnown.One;
+    break;
+  }
+
+  default:
+    break;
+  }
+}
+
 //===----------------------------------------------------------------------===//
 // Custom insertion
 //===----------------------------------------------------------------------===//

Modified: llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.h?rev=322986&r1=322985&r2=322986&view=diff
==============================================================================
--- llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.h (original)
+++ llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.h Fri Jan 19 12:49:05 2018
@@ -490,6 +490,14 @@ public:
                       SelectionDAG &DAG) const override;
   SDValue PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const override;
 
+  /// Determine which of the bits specified in Mask are known to be either
+  /// zero or one and return them in the KnownZero/KnownOne bitsets.
+  void computeKnownBitsForTargetNode(const SDValue Op,
+                                     KnownBits &Known,
+                                     const APInt &DemandedElts,
+                                     const SelectionDAG &DAG,
+                                     unsigned Depth = 0) const override;
+
   ISD::NodeType getExtendForAtomicOps() const override {
     return ISD::ANY_EXTEND;
   }